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authorJames Bottomley <James.Bottomley@HansenPartnership.com>2008-01-01 10:00:10 -0600
committerJames Bottomley <James.Bottomley@HansenPartnership.com>2008-01-11 18:29:22 -0600
commit465ff3185e0cb76d46137335a4d21d0d9d3ac8a2 (patch)
tree171068cd7d99600cd094c2eb72bac712649fd9eb /drivers/usb
parent11c3e689f1c3a73e3af7b0ea767b1b0626da8033 (diff)
[SCSI] relax scsi dma alignment
This patch relaxes the default SCSI DMA alignment from 512 bytes to 4 bytes. I remember from previous discussions that usb and firewire have sector size alignment requirements, so I upped their alignments in the respective slave allocs. The reason for doing this is so that we don't get such a huge amount of copy overhead in bio_copy_user() for udev. (basically all inquiries it issues can now be directly mapped). Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Diffstat (limited to 'drivers/usb')
-rw-r--r--drivers/usb/storage/scsiglue.c20
1 files changed, 10 insertions, 10 deletions
diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 7c9593b7b04e..dd8b13ef2414 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -81,6 +81,16 @@ static int slave_alloc (struct scsi_device *sdev)
*/
sdev->inquiry_len = 36;
+ /* Scatter-gather buffers (all but the last) must have a length
+ * divisible by the bulk maxpacket size. Otherwise a data packet
+ * would end up being short, causing a premature end to the data
+ * transfer. Since high-speed bulk pipes have a maxpacket size
+ * of 512, we'll use that as the scsi device queue's DMA alignment
+ * mask. Guaranteeing proper alignment of the first buffer will
+ * have the desired effect because, except at the beginning and
+ * the end, scatter-gather buffers follow page boundaries. */
+ blk_queue_update_dma_alignment(sdev->request_queue, (512 - 1));
+
/*
* The UFI spec treates the Peripheral Qualifier bits in an
* INQUIRY result as reserved and requires devices to set them
@@ -100,16 +110,6 @@ static int slave_configure(struct scsi_device *sdev)
{
struct us_data *us = host_to_us(sdev->host);
- /* Scatter-gather buffers (all but the last) must have a length
- * divisible by the bulk maxpacket size. Otherwise a data packet
- * would end up being short, causing a premature end to the data
- * transfer. Since high-speed bulk pipes have a maxpacket size
- * of 512, we'll use that as the scsi device queue's DMA alignment
- * mask. Guaranteeing proper alignment of the first buffer will
- * have the desired effect because, except at the beginning and
- * the end, scatter-gather buffers follow page boundaries. */
- blk_queue_dma_alignment(sdev->request_queue, (512 - 1));
-
/* Many devices have trouble transfering more than 32KB at a time,
* while others have trouble with more than 64K. At this time we
* are limiting both to 32K (64 sectores).